Composite connectors and methods of manufacturing the same

ABSTRACT

A method of manufacturing a composite (e.g. fibre-reinforced polymer) connector for a fluid transfer conduit includes: manufacturing a continuous fibre pre-form net that is shaped to comprise a hub-forming portion  156  and a flange-forming portion, the continuous fibre pre-form net comprising continuous fibre reinforcement and a common support layer to which the continuous fibre reinforcement is secured by being stitched thereto; placing the continuous fibre pre-form net into a mould, the mould being shaped such that the hub-forming portion forms a tubular hub portion which extends along a central axis and the flange-forming portion forms a flange portion which extends from the hub portion at an angle to the central axis; and introducing polymer into the mould so as to form a composite connector comprising the flange portion and the hub portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/536,361 filed Aug. 9, 2019 which claims priority to European PatentApplication No. 18275117.2 filed Aug. 10, 2018, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to composite (e.g. fibre-reinforcedpolymer) connectors, e.g. for connecting fluid transfer conduits toother structures, and to methods of manufacturing composite (e.g.fibre-reinforced polymer) connectors for fluid transfer conduits.

BACKGROUND

Fluid transfer conduits (e.g. fuel pipes) are typically connected toother fixed structures (e.g. inside aeroplane wings) using one or moreconnectors. To allow for movement of the fixed structure withoutinducing large stresses on the fluid transfer conduit itself (e.g. as awing flexes during flight), such connectors are designed to tolerate asmall amount of relative movement between the fluid transfer conduit andthe structure whilst still effectively supporting the conduit andsealing the connection. This is often achieved using an elastomericO-ring, on which the fluid transfer conduit “floats”, to seal theconnection while allowing a small amount of relative motion.

In many applications, such connectors are required to withstand largecircumferential loads (e.g. due to high internal pressures in a fluidtransfer conduit) as well as other stresses. To provide the requisitestrength while minimising part count, connectors are conventionallymachined from a single block of metal (usually aluminium). However, thisprocess results in a large amount of material being wasted (i.e. a veryhigh so-called buy-to-fly ratio).

Furthermore, fluid transfer conduits are increasingly being constructedfrom composite materials (e.g. fibre-reinforced polymers), in order tosave weight. However, when used with metallic connectors, compositefluid transfer conduits can experience various problems such as galvaniccorrosion and a reduced temperature operating window due to unequalthermal expansion.

More recently, therefore, an alternative manufacturing technique hasbeen developed whereby composite connectors are produced by injectionmoulding a thermoplastic matrix reinforced with randomly orientedchopped fibres (e.g. carbon/glass/aramid fibres). Because injectionmoulding is an additive process, it results in less wasted materialduring manufacture than conventional metal machining techniques. Inaddition, chopped-fibre reinforced composite parts are typically lighterthan their metal equivalents. However, chopped-fibre reinforcement doesnot exploit fully the potential strength of reinforcing fibres.

SUMMARY

According to one aspect of the present disclosure, there is provided acomposite (e.g. fibre-reinforced polymer) connector for a fluid transferconduit comprising: a hub portion comprising a tube which extendssubstantially parallel to a central axis; and a flange portion whichextends from the hub portion at an angle to the central axis; whereinthe hub portion and the flange portion each comprise a polymerreinforced with continuous fibre reinforcement and a common supportlayer to which the continuous fibre reinforcement is secured by beingstitched thereto; wherein at least some of the continuous fibrereinforcement extends between the hub portion and the flange portion.

Because of the high strength-to-weight ratio of continuousfibre-reinforced polymer, it will be appreciated by the person skilledin the art that the use of continuous fibre reinforcement in both thehub portion and the flange portion can produce a significantly strongerpart using the same amount of material compared to randomly-orientedfibre reinforcement or entirely metal parts. Correspondingly, an equallystrong part may be produced using less material, thus saving weight.

The composite connector according to the present disclosure may beproduced using additive processes. This means that there is littlematerial wasted during manufacture, especially compared to machiningtechniques used to construct conventional metal components. As a result,the cost of manufacturing a composite connector according to the presentdisclosure may be less than for an equivalent metal component, even ifthe underlying material costs are higher (due to less material going towaste).

When continuous fibre reinforcement is used to make a given component,the continuous fibre reinforcement may extend in one or more directionsthat are chosen to provide strength in a direction in which it isexpected the flange or hub portion will experience load. The layup ofthe continuous fibre reinforcement can be tailored to the loads expectedduring service. Many fibres may be oriented in a primary direction ofloading, and a lower proportion of fibres may therefore be oriented indirections in which the component experiences little load. Thisminimises the amount of material wasted when producing a part with agiven load capacity. In addition, as compared to discontinuous e.g.chopped fibre reinforcement, this means that the layup of the continuousfibre reinforcement can provide the flange portion with non-isotropicproperties.

Furthermore, when at least some of the continuous fibre reinforcementextends between the hub portion and the flange portion, the connector'sresistance to bending loads is improved as compared to previousconnectors (e.g. comprising chopped fibres). The orientation of thecontinuous fibre reinforcement that extends between the hub portion andthe flange portion can be controlled to maximise the benefits of fibrereinforcement running continuously through the connector, and adaptedfor a range of different connector geometries. The use of stitching tosecure the continuous fibre reinforcement to the common support layerassists with controlling the overall fibre layup.

When using randomly-oriented fibre reinforcement, no such tailoring canbe performed, and as such the amount of material required to provide therequired load resistance is increased. In addition, even when orientedin the direction of loading, chopped fibres inherently exhibit muchlower tensile strength than the equivalent amount of continuous fibrereinforcement. US 2016/0273696 describes an example of a composite partinjection-moulded from a thermoplastic matrix reinforced by choppedfibres.

As mentioned above, the composite connector of the present disclosuremay be produced using less material than conventional metal connectors,reducing component weight. In many applications, such as in theaerospace industry, any weight saving is highly advantageous as it canlead to significant fuel (and thus cost) savings over the lifetime of apart.

As is mentioned above, the use of stitching to secure the continuousfibre reinforcement to the common support layer provides control overthe fibre layup. The common support layer may be embedded in the samepolymer, e.g. matrix material, as the continuous fibre reinforcement.However the support layer may not be expected to contributesignificantly to the strength properties of the connector. In one ormore examples, the support layer may take the form of a fibre veil, forexample a veil of glass, carbon and/or aramid fibres. In one or morepotentially overlapping examples, a polyester or nylon thread may beused to stitch the continuous fibre reinforcement to the common supportlayer.

In one or more examples, the continuous fibre reinforcement may comprisemultiple layers stitched to the common support layer. The overallthickness of the composite connector may be dictated by the number oflayers used and the thickness of those layers. For the same compositethickness, it is envisaged that a larger number of layers is likely toprovide better product quality in any bends/radii of the connector (e.g.between the flange portion and the hub portion) than using fewer thickerlayers.

Alternatively, or in addition to comprising multiple layers stitched tothe common support layer, the composite connector may comprise aplurality of common support layers, to each of which one or more layersof continuous fibre reinforcement is stitched. The plurality of supportlayers may be arranged to reduce or eliminate the occurrence ofnon-reinforced (i.e. polymer-only) areas within the composite connector,e.g. by using different or complementary layers and/or by arranginglayers with an angular offset. As is explained in more detail below,this may be particularly advantageous when the composite connector isformed using pre-form nets, as it may be difficult to form athree-dimensional connector with continuous fibre reinforcement that iscontiguous throughout the connector (i.e. a connector with nounreinforced polymer-only regions) from a single two-dimensionalpre-form net.

In some examples, the flange portion comprises continuouscircumferentially-oriented fibre reinforcement. In such examples thecontinuous fibre reinforcement in the hub portion may comprise one ormore separate segments of continuous fibre reinforcement. In suchexamples, continuous fibre reinforcement from the one or more separatesegments extends into the flange portion. The plurality of separatesegments may be separated by one or more regions of unreinforcedpolymer.

Additionally or alternatively, the hub portion may comprise continuouscircumferentially-oriented fibre reinforcement, and optionally theflange portion may comprise a plurality of separate segments ofcontinuous fibre reinforcement. The plurality of separate segments maybe separated by one or more regions of unreinforced polymer.

The hub and flange portion may both comprise continuouscircumferentially-oriented fibre reinforcement. In such examples, thecontinuous circumferentially-oriented fibre reinforcement in the hub orflange portions may be provided by an additional support layer to whichthe continuous circumferentially-oriented fibre reinforcement has beensecured by being stitched thereto. The additional support layer maycomprise a tubular hub portion overwrap and/or may comprise an annularflange portion overwrap.

For instance, in examples where the hub portion comprises continuouscircumferentially-oriented fibre reinforcement and the flange portioncomprises a plurality of separate segments of continuous fibrereinforcement separated by one or more regions of non-reinforcedpolymer, the flange portion may further comprise an annular flangeoverwrap arranged to cover the regions of non-reinforced polymer andprovide continuous circumferentially-oriented fibre reinforcement in theflange portion.

Alternatively, in examples where the flange portion comprises continuouscircumferentially-oriented fibre reinforcement and the hub portioncomprises one or more separate segments of continuous fibrereinforcement separated by one or more regions of unreinforced polymer,the hub portion may further comprise an overwrap arranged to extendaround the hub portion to cover the regions of unreinforced polymer andto provide continuous circumferentially-oriented fibre in the hubportion.

The flange portion may comprise a tapering portion at an end of theflange portion proximal to the hub portion, the tapering portionextending at a lesser angle to the central axis of the hub portion thana non-tapering portion of the flange portion. In other words, the flangeportion may extend from the hub portion via this tapering portion.

The tapering portion may comprise continuous circumferentially-orientedfibre reinforcement. Additionally or alternatively, the tapering portionmay comprise continuous axially-oriented and/or helically-oriented fibrereinforcement. The non-tapering portion may comprise one or moreseparate segments of continuous fibre reinforcement. The hub portion maycomprise one or more separate segments of continuous fibrereinforcement. Thus, the composite connector may comprise a three-stagetapered connector.

The flange portion may comprise at least one fixing point (e.g. athrough-hole) which may be used along with a suitable fastening means(e.g. a nut and bolt) to secure the connector to a structure. The fixingpoint may be formed by drilling through the composite connector in apost-production step, but this would result in constituent fibres of thecontinuous fibre reinforcement being severed, which can reduce thestrength of the flange portion and thus the efficacy of the connector.In some examples, therefore, the fixing point is surrounded by unbrokenfibre reinforcement. The fibres thus divert around the perimeter of afixing point such as a through-hole. Stitching the continuous fibrereinforcement to the common support layer may assist with precise fibreplacement around such fixing points.

In one or more examples, the flange portion comprises at least onefixing point and the continuous fibre reinforcement is arranged in apattern around the fixing point, e.g. such that the continuous fibrereinforcement strengthens the fixing point. Conveniently, the continuousfibre reinforcement serves to assist in transmission of load betweenadjacent fixing points. In at least some examples, preferably thecontinuous fibre reinforcement at least partially encircles the fixingpoint(s). In some examples, the continuous fibre reinforcement may bearranged to encircle an adjacent pair of fixing points, e.g. at least 10times. An opening may be formed at each fixing point to enable theattachment of a fastener to the flange portion at the fixing point.Where the continuous fibre reinforcement passes around a fixing point,it may result in the formation of a hub of increased thickness. This maystrengthen the fixing point(s).

In some examples, the hub portion and the flange portion may eachcomprise a different polymer. Even with at least some continuous fibrereinforcement extending between the hub portion and the flange portion,the hub portion and the flange portion may each be over-moulded with adifferent polymer. However it is preferable that the hub portion and theflange portion comprise the same polymer, for example a common polymermatrix that extends from the hub portion to the flange portion. As isdescribed in more detail below, in one or more examples the connector isformed by moulding over a continuous fibre pre-form net that comprisesboth a hub-forming portion and a flange-forming portion. For example, aninjection moulding or resin transfer moulding process may be used tomould the same polymer over a continuous fibre pre-form net that formsthe continuous fibre reinforcement of the hub and flange portions.

In some examples, the polymer is preferably a thermosetting polymer,such as a polyester, epoxy or phenolic resin. Thermosetting polymersprovide high strength, are easy to work with and can be less expensivethan thermoplastic polymers.

Alternatively, in some other examples, the polymer is a thermoplasticpolymer, e.g. polyether ether ketone (PEEK), polyetherketoneketone(PEKK), polyetherketone (PEK) or another polymer that is part of thepolyaryletherketone (PAEK) family.

The polymer may optionally include one or more non-fibre materialadditives. For example, the polymer may include small quantities of oneor more non-fibre material additives intended to alter one or morenon-structural properties of the polymer, such as viscosity, thermal orelectrical conductivity, radiation sensitivity, colour, fire or chemicalresistance etc.

For example, in aircraft fuel systems, it is important to control theconductivity of the composite connector. Ideally the fuel system (i.e.comprising pipes are connectors) is insulating enough to avoid becomingthe preferred path for lighting conduction, whilst conductive enough toavoid static build-up due to fuel flow. Adding a particular amount of aconductive additive (e.g. carbon black) to the polymer duringmanufacture allows the desired level of conductivity to be achieved.Such an additive is ideally present throughout the component (i.e. inboth the flange portion and the hub portion), although this is notessential.

For example, if carbon fibre reinforcement is used in the hub portionbut the flange portion contains no carbon fibre reinforcement (e.g. inexamples where the flange portion comprises unreinforced polymer), acarbon black additive may only need to be present in the flange portion(as the carbon fibres in the hub portion are already conductive).

To control the conductivity of a fuel system, it may not be necessary tocontrol the conductivity of both the pipe(s) and the connector(s). Itmay be sufficient, in at least some cases, for the conductivity of onlythe pipe(s) to be controlled (e.g. by adding a certain concentration ofcarbon black during pipe manufacture). The connector then simply needsto comprise a minimum level of conductivity for the desired overallconductivity to be achieved. Alternatively, the conductivity of theconnector(s) may be controlled and used with a pipe with a simpleminimum conductivity.

The angle to the central axis at which the flange portion extends ispreferably greater than 45°, and the flange portion is furtherpreferably substantially perpendicular to the central axis of the hubportion, i.e. at about 90°, to enable secure attachment to a surfacenormal to the central axis. In some examples the entire flange portionmay not extend at the same angle to the central axis but may be shapedto accommodate the shape of a particular structure.

“Continuous” fibre reinforcement is used herein to refer to fibrereinforcement in which at least some individual constituent filamentshave a substantial length, i.e. they are not short “chopped fibres” ordiscontinuous fibres. In at least some examples, the fibre reinforcementmay be considered to be “continuous” when the fibres or filaments have alength on the same scale as the part they are reinforcing. This meansthat the fibre reinforcement is substantially “continuous” when itextends uninterrupted across a given dimension of a part, such as alength, radius or circumference.

The use of continuous fibre reinforcement within the hub and flangeportions allows the coefficient of thermal expansion of the compositeconnector to be tuned to a desired value. For example, the coefficientof thermal expansion of the composite connector may be made tosubstantially match that of a corresponding fluid transfer conduit.

In at least some examples, the hub portion comprises regions consistingof unreinforced polymer, i.e. with no continuous fibre reinforcement.However, in at least some other examples, the hub portion comprisescontinuous circumferentially-oriented fibre reinforcement. In additionto the strength benefits, utilising continuouscircumferentially-oriented fibre reinforcement in the hub portion alsoenables the coefficient of thermal expansion (i.e. the “hoop” CTE) ofthe hub portion to be closely matched to that of a fluid transferconduit to which it may be connected.

Fluid transfer conduits for which the connector of the presentdisclosure is particularly suitable are composite parts manufacturedfrom fibre-reinforced polymers comprising a high proportion ofcontinuous circumferentially-oriented fibres. This maximises the hoopstrength and thus the internal pressure tolerance of the conduit,something which is particularly important in high pressure systems suchas fuel pipes, while minimising weight. Because of the high proportionof circumferential fibre in such composite conduits, when the fluidtransfer conduit is subject to a change in temperature (e.g. due tochanging ambient conditions), the radial expansion is dominated by theexpansion of the fibre reinforcement. Fibres used as reinforcement insuch materials typically have a very low CTE compared to the polymermatrix. For example, glass fibres have a CTE of around 1.6-2.9×10-6 K-1and carbon fibres have a CTE which is very close to zero (and may evenbe negative, e.g. roughly −0.5×10-6 K-1), while a typical polymer resinhas a CTE of ˜50×10-6 K-1 (for comparison, aluminium has a CTE of˜23×10-6 K-1). As a result, the circumferential (hoop) thermal expansionof a fibre-reinforced polymer conduit with continuous circumferentialfibre is usually low.

Injection-moulded, randomly-oriented chopped fibre-reinforcedcomposites, in comparison, have a hoop CTE which is dominated by the CTEof the resin matrix—i.e. much higher than that of the fibre-reinforcedpolymer (FRP) conduits described above. Metal connectors also sufferrelatively high thermal expansion.

Conventional connectors therefore, when used with fibre-reinforcedpolymer conduits, can only be used within a small temperature operatingenvelope. Differential expansion of the connector and the conduit whensubject to temperatures outside this envelope can risk the integrity ofthe seal and/or the entire connection. Or, the requirement toaccommodate such temperature variations and differing CTEs puts designconstraints on other elements such as the O-ring. A similar issue ariseswhen a connector has a different stiffness to that of a conduit.

However, as mentioned above, because the hub portion in examples of thepresent disclosure comprises continuous circumferentially-oriented fibrereinforcement, its hoop CTE (and its stiffness) can be more closelymatched to that of a given fluid transfer conduit. Matching the CTEallows relative expansion (of the connector relative to the conduit)during use to be minimised over a wider range of temperatures,increasing the applicability and reliability of the part. In someexamples, therefore, the composition and orientation of the continuouscircumferentially-oriented fibre reinforcement within the hub portion isselected such that the CTE (i.e. the hoop CTE) of the hub portionmatches that of a fluid transfer conduit, formed from FRP, which isconnected to the hub portion in use. Additionally or alternatively, thecomposition and orientation of the fibre reinforcement within the hubportion is selected such that the stiffness of the hub portionsubstantially matches that of the fluid transfer conduit.

The hub portion is preferably arranged to fit onto or into a fluidtransfer conduit, e.g. concentric therewith, with a conduit fitting overan outer diameter of the hub portion or inside an inner diameter of thehub portion. The flange portion is preferably arranged to attach to afurther structure and may comprise one or more attachment pointsthereto.

There is further disclosed a connection system comprising a compositeconnector as disclosed herein and a FRP fluid transfer conduit connectedto the hub portion. In one or more examples, the composition andorientation of the continuous fibre reinforcement at least within thehub portion is selected such that the coefficient of thermal expansionof the hub portion substantially matches that of the fluid transferconduit. Additionally or alternatively, the composition and orientationof the fibre reinforcement within the hub portion is selected such thatthe stiffness of the hub portion substantially matches that of the fluidtransfer conduit.

As mentioned above, an elastomeric O-ring may be used to seal aconnection between the connector and a fluid transfer conduit. In suchcases the O-ring may be positioned between an outer surface of the fluidtransfer conduit and an inner surface of the hub portion (or,conversely, between an inner surface of the conduit and an outer surfaceof the hub portion), to seal the connection. Optionally, the elastomericis seated between a pair of retaining ridges that allow for axialmovement between the fluid transfer conduit and the hub portion. Thestrong and stiff hub portion keeps the O-ring tightly pressed radiallybetween the inner (or outer) surface of the hub portion and the outer(or inner) surface of the fluid transfer conduit, ensuring the integrityof the seal.

In one or more examples, matching of the coefficient of thermalexpansion and/or stiffness may be achieved by matching the compositionand angle of the continuous circumferentially-oriented fibrereinforcement within the hub portion to the composition and angle ofcontinuous circumferentially-oriented reinforcing fibre within the FRPconduit. The continuous circumferentially-oriented fibre reinforcementin the hub portion may therefore have substantially the same fibre angleas the continuous circumferentially-oriented fibre reinforcement in theconduit. In some examples these fibre angles may differ by no more than15°, no more than 10°, and, preferably, by no more than 5°.

In the hub portion, the continuous circumferentially-oriented (hoop)fibre reinforcement typically makes an angle of more than 60° to thecentral axis. In preferred examples the continuouscircumferentially-oriented fibre reinforcement extends at an angle ofmore than 80° to the central axis, e.g. at least 85°, or even at orclose to 90°. A high angle maximises the hoop strength provided by thecontinuous circumferentially-oriented fibre reinforcement.

In some examples the hub portion comprises a mixture of layers ofcontinuous axially-oriented and/or helically-oriented fibrereinforcement and layers of the continuous circumferentially-orientedfibre reinforcement, e.g. alternating layers of continuousaxially-oriented and circumferentially-oriented fibre reinforcement.This provides the hub portion with uniform strength and mitigatesdelamination during use. Mixing layers of continuous fibre reinforcementwith different orientations may also prevent large residual stressesbeing produced during manufacture, which can severely weaken theconnector.

The hub portion preferably comprises a tube with a substantiallycircular cross-section (i.e. the hub portion comprises a cylinder). Acircular cross-section maximises the hoop strength of the hub portionand can be easier to manufacture. In some examples, however, the tubemay have a rectangular, other polygonal or an elliptical cross-section,amongst other possible shapes. Preferably the hub portion has across-section which matches that of a fluid transfer conduit to which itis suitable for connecting. In a connection system as disclosed above,the hub portion may have substantially the same cross-section as thefluid transfer conduit.

The present disclosure extends to a method of manufacturing a composite(e.g. fibre-reinforced polymer) connector for a fluid transfer conduit,the method comprising: manufacturing a continuous fibre pre-form netthat is shaped to comprise a hub-forming portion and a flange-formingportion, the continuous fibre pre-form net comprising continuous fibrereinforcement and a common support layer to which the continuous fibrereinforcement is secured by being stitched thereto, wherein at leastsome of the continuous fibre reinforcement extends between thehub-forming portion and the flange-forming portion; placing thecontinuous fibre pre-form net into a mould, the mould being shaped suchthat the hub-forming portion forms a tubular hub portion which extendsalong a central axis and the flange-forming portion forms a flangeportion which extends from the hub portion at an angle to the centralaxis; and introducing polymer into the mould so as to form a compositeconnector comprising the flange portion and the hub portion.

Securing the continuous fibre reinforcement to a support layer holds thecontinuous fibre reinforcement together in the pre-form net and in adesired position/orientation when the pre-form net is placed into themould. This allows a connector with the desired properties (e.g. fibredensities and/or orientations) to be manufactured more easily andreliably. The use of stitching in the pre-form net can allow precisefibre reinforcement placement, making it possible to achieve complicatedshapes with precise fibre orientation. In one or more examples,manufacturing the continuous fibre pre-form net may comprise a tailoredfibre placement technique.

It will be appreciated that the continuous fibre pre-form net may be asubstantially two-dimensional e.g. planar structure that is shaped tocomprise a hub-forming portion and a flange-forming portion. The mouldmay have a three-dimensional shape that is chosen to correspond with theshape of the continuous fibre pre-form net, such that the hub-formingportion is converted into the three-dimensional shape of the tubular hubportion and the flange-forming portion is converted into thethree-dimensional shape of the flange portion. There may be a number ofdifferent shapes for the continuous fibre pre-form net that result insubstantially the same or similar shapes for the hub portion and flangeportion. Placing the continuous fibre pre-form net into the mould maycomprise conforming the continuous fibre pre-form net to the mould, forexample through bending and/or manipulating the continuous fibrepre-form net. The flange-forming portion and/or the hub-forming portionmay comprise a series of interconnected segments which are arranged tofacilitate conforming the pre-form net to the mould.

In one set of examples, the flange-forming portion may comprise anannular portion which surrounds the hub-forming portion. In suchexamples the hub-forming portion may comprise one or more tabs whichextend from an inner edge of the annular portion. The continuous fibrepre-form net may have an overall disc-like shape. In such examples,placing the pre-form net into the mould comprises folding out the one ormore tabs such that they extend at an angle to the annularflange-forming portion. The mould may be shaped, for example bycomprising a cylindrical surface oriented along the central axis, suchthat the tabs extend along the central axis to form at least part of thetubular hub portion. As is described further below, a hub-formingoverwrap may also be placed in the mould around the central axis.

Alternatively, the hub-forming portion may comprise a contiguous sheet(not comprising separate segments or tabs—e.g. a rectangular sheet) andthe flange—forming portion may comprise one or more tabs extending froman edge of the contiguous sheet. In such examples, placing thecontinuous fibre pre-form net into the mould comprises wrapping thehub-forming portion into a tubular shape around the central axis to forma hub portion, and folding the one or more tabs of the flange-formingportion outwards such that they extend at an angle to the central axisto form a flange portion.

In at least some such examples, the hub-forming portion preferablycomprises continuous fibre reinforcement which is arranged to formcontinuous circumferentially-oriented fibre reinforcement in the hubportion. Preferably, manufacturing the continuous fibre pre-form netfurther comprises arranging the continuous fibre reinforcement in thehub-forming portion of the continuous fibre pre-form net to formcontinuous circumferentially-oriented fibre reinforcement in the hubportion. The continuous circumferentially-oriented fibre reinforcementpreferably comprises at least some individual constituent filamentswhich extend around a significant fraction of the circumference of thehub portion, e.g. extending 90°, 180°, 270° or more around the centralaxis of the hub portion.

Continuous circumferentially-oriented fibre reinforcement in the hubportion provides increased circumferential (hoop) strength, improvingthe connector's resistance to high hoop loads (e.g. due to high pressurefluid within a fluid transfer conduit positioned within the hubportion). Continuous circumferentially-oriented fibre reinforcement inthe hub portion thus enables further weight savings, by enabling a partwith a required strength to be produced with less material.

In addition to weight savings, the use of continuouscircumferentially-oriented fibre reinforcement within the hub portion ofthe connector also confers other benefits. For example, the continuouscircumferentially-oriented fibre reinforcement may stiffen the hubportion. When fluid at high pressure is passed through a fluid transferconduit connected to the connector, this increased stiffness mitigatesradial expansion of the connector, ensuring that a good connection andseal with the fluid transfer conduit is maintained at all times.

In addition, or alternatively, manufacturing the continuous fibrepre-form net may comprise arranging the continuous fibre reinforcementin the hub-forming portion of the continuous fibre pre-form net to formcontinuous axially-oriented and/or helically-oriented fibrereinforcement in the hub portion.

As mentioned above, placing the continuous fibre pre-form net into amould may comprise conforming the continuous fibre pre-form net to themould, e.g. by bending, folding or otherwise manipulating the continuousfibre pre-form net into a three-dimensional shape of the mould. However,due to the limitations inherent in forming a three-dimensional structurefrom a net, when the continuous fibre pre-form net is placed into themould, the mould may comprise one or more regions into which thecontinuous fibre pre-form net does not extend, but to which the polymernevertheless permeates when it is introduced. This leaves the resultingcomposite connector with regions of unreinforced polymer betweensegments of continuous fibre reinforcement.

For instance, in examples where the flange-forming portion comprises anannular portion and the hub-forming portion comprises one or more tabsthat extend inwards from an inner edge of the annular portion, gapsbetween the one or more tabs may appear when they are folded to form aconnector with a flange portion that extends from the hub portion at anangle to the central axis (i.e. unreinforced regions may appear in thehub portion such that the resulting connector does not comprise atubular hub portion with contiguous continuous fibre reinforcement).

While, at least in some examples, regions of unreinforced polymer in thecomposite connector may be acceptable (e.g. in applications with lowload requirements, or if the regions of unreinforced polymer arecoincident with regions requiring a low load capacity), it may bebeneficial to reduce the size or prevalence of, or to entirelyeliminate, such regions. In some examples, therefore, the continuousfibre pre-form net comprises one or more overlapping tabs. Suchoverlapping tabs allow a planar net to be formed into a threedimensional connector with fewer or smaller regions of unreinforcedpolymer. For example, the hub-forming portion of such a continuous fibrepre-form net may comprise two or more tabs which overlap. Preferably,when the continuous fibre pre-form net is placed into the mould, theoverlapping tabs are spread such that they no longer overlapsubstantially.

Manufacturing the pre-form net may comprise manufacturing the commonsupport layer prior to any stitching. The common support layer maycomprise a single piece of support material (e.g. stamped out of alarger sheet), but in some examples the common support layer may beformed by joining together several separate pieces of support material(e.g. a fibre veil). This may facilitate the forming of overlapping tabsin the pre-form net in some examples. The pieces may be joined viastitching, preferably using a non load-bearing thread such as apolyester embroidery thread.

Alternatively, or additionally, the method may comprise manufacturing aplurality of continuous fibre pre-form nets. Each of the plurality ofcontinuous fibre pre-form nets may comprise a hub-forming portion and aflange-forming portion. In some such examples, the method may compriseplacing the plurality of continuous fibre pre-form nets into the mouldso as to minimise or eliminate regions of the mould into which at leastone continuous fibre pre-form net does not extend. This may, forexample, be achieved by positioning one continuous fibre pre-form netover another and/or offsetting (e.g. angularly offsetting) the pluralityof continuous fibre pre-form nets within the mould, to mitigate gaps incontinuous fibre pre-form coverage within the mould.

The plurality of continuous fibre pre-form nets may comprise a firstcontinuous fibre pre-form net and a second continuous fibre pre-formnet. The first continuous fibre pre-form net may comprise a hub-formingportion and a flange-forming portion, wherein the flange-forming portioncomprises an annular portion which surrounds the hub-forming portion andthe hub-forming portion comprises one or more tabs which extend from aninner edge of the annular portion. The second continuous fibre pre-formnet may comprise a hub-forming overwrap (e.g. a rectangular sheet). Insuch examples, placing the plurality of continuous fibre pre-form netsinto the mould comprises folding out the one or more tabs of the firstcontinuous fibre pre-form net such that they extend at an angle to theflange-forming portion and wrapping the hub-forming overwrap around thehub-forming portion of the first continuous fibre pre-form net such thatthe finished connector comprises continuous circumferentially-orientedfibre reinforcement in the hub portion, provided by the hub-formingoverwrap.

For example, the method may comprise manufacturing two continuous fibrepre-form nets, each comprising a flange-forming portion comprising anannular portion and a hub-forming portion comprising one or more tabsextending from an inner edge of the annular portion. The two continuousfibre pre-form nets may be placed into the mould with the annularportions aligned, but with an angular offset, such that gaps in thehub-forming portions of one continuous fibre pre-form net are at leastpartially covered by the tabs of the other continuous fibre pre-formnet. This reduces, and may eliminate, regions of unreinforced polymer inthe hub portion of the finished connector.

The continuous fibre reinforcement that extends between the hub-formingportion and the flange-forming portion may be arranged to facilitate theflange-forming portion being bent or folded relative to the hub-formingportion (e.g. to conform to the shape of the mould). This may compriseslack being built into the continuous fibre reinforcement stitched tothe continuous fibre pre-form net at or near a boundary between thehub-forming and flange-forming portions. This slack enables theflange-forming and hub-forming portions to be easily manipulated into adesired position relative to one another to form the flange and hubportions when the continuous fibre pre-form net is placed into themould.

By moulding polymer around the continuous fibre pre-form net, the flangeportion and the hub portion may be integrated by the moulding process.As is mentioned above, preferably the same polymer is moulded around thecontinuous fibre pre-form net. This manufacturing method thereforeavoids a polymer joint between two composite parts or pre-impregnatedfibre forms that are subsequently overmoulded or co-moulded to form thehub and flange portions of the composite connector.

In one or more examples, manufacturing the continuous fibre pre-form netmay comprise arranging the continuous fibre reinforcement in multipleorientations, for example in circumferential and/or radial and/or axialorientations. Such fibre placement can be exploited to optimise thefibre orientations in the resulting hub and flange portions. Forexample, the continuous fibre reinforcement in the hub-forming portionmay be arranged in the continuous fibre pre-form net to provide somesubstantially axially-orientated fibres in the hub portion that couldnot be provided by other manufacturing techniques such as filamentwinding.

In one or more examples, manufacturing the continuous fibre pre-form netmay further comprise stitching multiple layers to the common supportlayer. As is mentioned above, the overall thickness of the compositeconnector may be dictated by the number of layers used and the thicknessof those layers.

In one or more examples, manufacturing the continuous fibre pre-form netmay comprise forming at least one fixing point for the flange portion byarranging the continuous fibre reinforcement in the flange-formingportion in a pattern around the fixing point, e.g. such that thecontinuous fibre reinforcement strengthens the fixing point. In at leastsome examples, preferably the continuous fibre reinforcement is arrangedto at least partially encircle the fixing point(s)

In one or more examples, introducing polymer into the mould may comprisea resin transfer moulding (RTM) process or vacuum infusion process,wherein preferably the polymer comprises a thermosetting polymer. Insome examples, the method may further comprise curing the compositeconnector in the mould. In some examples, the method may compriseheating the mould to pre-cure the composite connector and/or apost-moulding curing step may be used after removing the connector fromthe mould.

However, as RTM or vacuum infusion processes can require relatively longcure times, in some other examples, introducing polymer into the mouldcomprises an injection moulding process, wherein preferably the polymercomprises a thermoplastic polymer. Injection moulding typically has amuch shorter cure time, although the material costs may be greater.

In various examples according to the present disclosure, the continuousfibre reinforcement may comprise any suitable fibre material. Forexample, the continuous fibre reinforcement may consist of one or moreof glass, carbon or synthetic (e.g. aramid) fibres. Glass fibrereinforcement may be preferred for connectors intended to be used withfluid transfer conduits (e.g. fuel pipes) made of glass fibre-reinforcedcomposite.

The present disclosure refers throughout to a composite connectorcomprising a hub portion and a flange portion. It will be appreciatedthat a given connector may comprise more than one flange portion per hubportion, or more than one hub portion per flange portion. Anysingle-ended, double-ended or multiple port connector is included withinthis disclosure.

Features of any example described herein may, wherever appropriate, beapplied to any other example described herein. Where reference is madeto different examples or sets of examples, it should be understood thatthese are not necessarily distinct but may overlap.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain examples of the present disclosure will now be described withreference to the accompanying drawings in which:

FIG. 1 is a cross sectional view of the connection between a connectorand a fluid transfer conduit;

FIG. 2 shows a schematic perspective view of a composite connector for afluid transfer conduit according to an example of the presentdisclosure;

FIG. 3 shows a plan view of a continuous fibre pre-form net used tomanufacture the composite connector of FIG. 2 ;

FIG. 4 shows a composite connector for a fluid transfer conduitaccording to another example of the present disclosure;

FIG. 5 shows a continuous fibre pre-form net used to manufacture thecomposite connector of FIG. 4 ;

FIG. 6 shows another example of a composite connector;

FIGS. 7 and 8 show a corresponding pre-form net used to manufacture thecomposite connector of FIG. 6 ;

FIG. 9 shows another example of a composite connector;

FIG. 10 shows a corresponding pre-form net used to manufacture thecomposite connector of FIG. 9 ;

FIG. 11 shows a cross sectional view of examples of composite connectorsformed from the pre-form net of FIG. 10 ;

FIG. 12 shows a cross sectional view of examples of composite connectorsformed from the pre-form net of FIG. 10 ;

FIG. 13 shows a further example of a pre-form net used to manufacturethe composite connector of FIG. 9 ;

FIG. 14 is a cross sectional view of another example of a compositeconnector;

FIG. 15 shows an example of a hub overwrap pre-form net used tomanufacture the composite connector of FIG. 14 ;

FIG. 16 is a cross sectional view of another example of a compositeconnector;

FIG. 17 is an enlarged view of continuous fibre reinforcement in apre-form net according to one or more of the examples disclosed herein;

FIG. 18 is a cross sectional view of another example of a compositeconnector;

FIG. 19 shows a further example of a pre-form net used to manufacturethe composite connector of FIG. 18 ;

FIG. 20 is a cross sectional view of a mould used to manufacture acomposite connector; and

FIG. 21 shows a connection system according to an example of the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 shows the interface between a connector 2 and a cylindrical fluidtransfer conduit 4 that extends parallel to a central axis C. Theconnector 2 comprises a cylindrical hub portion 6, which also extendsparallel to the central axis C, and a flange portion 8, which extendsfrom an end of the hub portion 6 in a direction perpendicular to thecentral axis C. The flange portion 8 further comprises a through-hole10, by which the connector 2 may be secured to another structure, e.g.an aircraft wing rib.

The hub portion 6 encloses a connection portion 12 of the fluid transferconduit 4. An elastomeric O-ring 14 is located between the hub portion 6and the connection portion 12, retained between an inner wall of the hubportion 6 and an outer wall of the fluid transfer conduit 4. The O-ring14 is confined by two retaining ridges 16 which extend radially outwardsfrom the connection portion 10 of the fluid transfer conduit 4.

The O-ring 14 provides a seal between the connector 2 and the conduit 4,such that fluid may flow along the conduit 4 and into the connector 2without escaping. In addition, the configuration of O-ring 14 betweenthe two retaining ridges 16 of the connection portion 12 and the hubportion 6 allows the fluid transfer conduit 4 to move a small distancein the direction of the central axis C relative to the connector 2without compromising the seal. This enables a structure to which theconnector 2 is secured to move or flex a small amount without impartinglarge stresses on the conduit 4 (as would be the case if the connector 2was rigidly attached to the conduit 4). Instead, the conduit 4 “floats”on the O-ring 14 such that it can slide longitudinally a small distancewithout breaking the seal. For example, the structure to which theconnector 2 is attached may be an aircraft wing rib, which is designedto move a small amount during flight as the wing flexes due toaerodynamic load and/or temperature fluctuations. The fluid transferconduit 4 may comprise a fuel pipe located within the wing which musttherefore be able to cope with the wing flex during flight.

FIG. 2 is a schematic perspective view of a composite connector 102according to an example of the present disclosure. The connector 102comprises a cylindrical hub portion 106 which extends parallel to acentral axis C and a flange portion 108 which extends perpendicularlyfrom an end of the hub portion 106.

Continuous fibre reinforcement 110 extends between the hub portion 106and the flange portion 108. This strengthens the transition between thehub portion 106 and the flange portion 108 and thus increases theability of the connector 102 to withstand bending loads (e.g. due towing flex or inertial loads during flight). The flange portion 108comprises four through holes 114 (although only three are visible inFIG. 2 ), around which the continuous fibre reinforcement 110 diverts.The fibre reinforcement 110 may encircle entirely the through holes 114,possibly several times.

A connection system comprising the connector 102 of FIG. 2 and afibre-reinforced polymer fluid transfer conduit is shown in FIG. 21 .

FIG. 3 shows an example of a continuous fibre pre-form net 150 used toform the composite connector 102. The net 150 comprises an annularflange-forming portion 158 which surrounds a hub-forming portion 156.The hub-forming portion 156 is split into four separate segments or tabswhich extend radially inward from an inner edge of the flange-formingportion 158. The continuous fibre pre-form net 150 comprises a planarcommon support layer 151, to which the continuous fibre reinforcement110 is secured via stitching 153 (only a small section of stitching isshown to aid clarity). Securing the continuous fibre reinforcement 110to the common support layer 151 by stitching 153 means it can bepositioned in any direction or orientation and held in place. In thisexample, the stitching 153 comprises a polyester thread, although othermaterials may be used (e.g. nylon). The continuous fibre reinforcement110 extends circumferentially in the flange-forming section 158 andextends into each of the segments of the hub-forming section 156 (thecontinuous fibre reinforcement 110 is only shown partially in FIGS. 2and 3 for clarity).

The pre-form net 150 comprises four through holes 164, defined by holesin the common support layer 151 and reinforced by being encircled by thecontinuous fibre reinforcement 110. These will become the through holes114 in the finished connector 102.

As explained below in further detail, the composite connector 102 isformed by placing the pre-form net 150 into a mould, with each of thesegments of the hub-forming portion 156 bent up to be perpendicular tothe annular flange-forming portion 158. A polymer matrix is thenintroduced into the mould to form the composite connector 102.

As seen in FIG. 2 , bending the segments of the hub-forming portion 156to be perpendicular to the annular flange-forming portion 158 results inunreinforced joins and/or gaps 112 comprising non-reinforced polymerappearing in the hub portion 106 of the composite connector 102. Theseunreinforced joins and/or gaps 112 correspond to regions of the mould towhich the pre-form net 150 does not extend but to which the polymerintroduced into the mould has permeated regardless. As will be explainedin more detail below, the strength in these unreinforced regions can beimproved, if desired, by the addition of a separate preform layer (suchas that shown in FIG. 15 ), e.g. which can be formed into a cylinder foruse in the hub portion 106 only and eliminates any regions without fibrereinforcement.

FIG. 4 shows a schematic perspective view of a composite connector 202according to another example of the present disclosure. The connector202 comprises a cylindrical hub portion 206 which extends parallel to acentral axis C and a flange portion 208 which extends perpendicularlyfrom an end of the hub portion 206. Continuous fibre reinforcement 210extends between the hub portion 206 and the flange portion 208.

FIG. 5 shows a pre-form net 250 used to form the composite connector202. The net 250 comprises a rectangular hub-forming portion 256, fromone edge of which a flange-forming portion 258 extends. Theflange-forming portion 258 comprises a plurality of tabs. The continuousfibre reinforcement 210 extends from the hub-forming portion 256 intoeach of the tabs of the flange-forming portion 258. The continuous fibrepre-form net 250 comprises a planar common support layer 251, to whichthe continuous fibre reinforcement 210 is secured via stitching 253(only a small section of stitching is shown in FIG. 5 to aid clarity).

The composite connector 202 is formed by placing the pre-form net 250into a mould, with the hub-forming portion 256 rolled into a tubularshape and the tabs of the flange-forming portion 258 bent outwards suchthat they extend perpendicularly from the hub-forming portion 256. Thetabs will go on to form the annular flange portion 208 of the finishedconnector. A polymer matrix is then introduced into the mould to formthe composite connector 202.

As seen in FIG. 4 , bending the tabs of the flange-forming portion 258outwards results in the annular flange portion 208 comprising aplurality of unreinforced gaps 212 made up of non-reinforced polymer.These unreinforced gaps 212 correspond to regions of the mould to whichthe pre-form net 250 does not extend but to which the polymer introducedto the mould has nevertheless permeated.

As mentioned above, the connectors 102, 202 comprise unreinforced gaps112, 212 (in the hub portion 106 and the flange portion 208respectively) where no continuous fibre reinforcement 110, 210 ispresent (i.e. comprising non-reinforced polymer). It may be desirable toreduce the size of or entirely eliminate these unreinforced regionswherever possible. FIG. 6 shows a composite connector 302 in which thesegaps have been reduced. FIG. 7 shows a pre-form net 350 used to form theconnector 302.

The composite connector 302 comprises a cylindrical hub portion 306which extends parallel to a central axis C and a flange portion 308which extends perpendicularly from an end of the hub portion 306.Continuous fibre reinforcement 310 extends between the hub portion 306and the flange portion 308.

The pre-form net 350 comprises an annular flange-forming portion 358which surrounds a hub-forming portion 356. Somewhat similarly to thepre-form net 150 shown in FIG. 3 , the hub-forming portion 356 comprisesa plurality of separate segments or tabs which extend radially inwardsfrom an inner edge of the flange-forming portion 358 (only four tabs areshown in FIG. 7 to aid clarity).

However, in contrast to the net 150 shown in FIG. 3 , the tabs of thehub-forming portion 356 overlap in this example. The pre-form net 350comprises a common support layer 351 to which the continuous fibrereinforcement 310 is secured by stitching (not shown in FIG. 7 ). Thecontinuous fibre reinforcement 310 extends circumferentially in theflange-forming section 358 and extends into each tab of the hub-formingsection 356 (although the continuous fibre reinforcement 310 is onlyshown partially in FIGS. 6 and 7 for clarity).

To enable the tabs of the hub-forming portion 356 to overlap, the commonsupport layer 351 comprises a multi-piece support layer formed byjoining together several separate pieces (not shown) of a supportmaterial (e.g. a fibre veil). The pieces are joined by stitching using anon load-bearing thread such as a polyester embroidery thread.

As mentioned above, the tabs of the hub-forming portion 356 overlap.During manufacture, each tab is lifted in turn to allow fibrereinforcement 310 to be stitched to the tab(s) underneath. This ensuresthat the fibre reinforcement 310 extends into each tab.

FIG. 8 shows an example of the placement and orientation of thecontinuous fibre reinforcement 310 in the pre form net 350. FIG. 8 showsa portion of the continuous fibre reinforcement 310 a extending alongand across a tab of the hub-forming portion 356, a portion of thecontinuous fibre reinforcement 310 b running circumferentially andradially in the flange-forming portion 358, and a portion of thecontinuous fibre reinforcement 310 c encircling a through-hole 312 inthe flange-forming portion 358.

As can be seen in FIG. 6 , the overlapping tabs in the hub-formingportion 356 of the pre-form net 350 mean that the resulting compositeconnector 302 does not feature unreinforced gaps comprisingnon-reinforced polymer.

FIG. 9 shows a composite connector 402 comprising a cylindrical hubportion 406 which extends parallel to a central axis C and a flangeportion 408 which extends perpendicularly from an end of the hub portion406. Continuous fibre reinforcement 410 extends between the hub portion406 and the flange portion 408.

A pre form net 450 used to form the composite connector 402 is shown inFIG. 10 . The pre-form net 450 comprises an elongate rectangularhub-forming portion 456, from one edge of which a flange-forming portion458 extends. The flange-forming portion 458 comprises a plurality oftrapezoidal tabs. The continuous fibre reinforcement 410 extends fromthe hub-forming proton 456 into each of the tabs of the flange-formingportion 458. The continuous fibre pre-form net 450 comprises a planarcommon support layer 451, to which the continuous fibre reinforcement410 is secured via stitching (not shown).

The composite connector 402 is formed by placing the pre-form net 450into a mould, with the hub-forming portion 456 rolled into a tubularshape to form the hub portion 406 and the tabs of the flange-formingportion 458 bent outwards such that they extend perpendicularly from thehub-forming portion 456 to form the flange portion 408. As shown incross section in FIG. 11 , the pre-form net 450 is wound around thecentral axis several times (e.g. two), such that the hub portion 406 ofthe composite connector comprises several layers of the hub-formingportion 456 (i.e. several layers of the support 451 and the fibrereinforcement 410 which is stitched thereto). Alternatively, as shown inFIG. 12 , two pre-form nets 450 a,b may be placed in the mould with anangular offset.

The flange portion 408 of the composite connector thus comprises several(e.g. two) layers 408 a, 408 b of the flange-forming portion 458. Thetabs in subsequent layers 408 a, 408 b of the flange portion 408 areoffset such that gaps in one layer (e.g. 408 a) are covered by the tabsof another (e.g. 408 b), as shown in FIG. 9 . As such, the flangeportion 408 of the finished connector 402 does not comprise regions ofnon-reinforced polymer.

An alternative example of a pre-form net 480 which may be used to formthe composite connector 402 is shown in FIG. 13 . The pre-form net 480comprises a rectangular hub-forming portion 486, from one edge of whicha flange-forming portion 488 extends. The flange-forming portion 488comprises a plurality of triangular tabs. Continuous fibre reinforcement410 extends from the hub-forming portion 486 into each of the tabs ofthe flange-forming portion 488. The continuous fibre pre-form net 480comprises a common support layer 481, to which the continuous fibrereinforcement 410 is secured via stitching (not shown). The tabs of theflange-forming portion 488 are overlapping, such that when the pre-formnet 480 is formed into the composite connector 402 no gaps comprisingnon-reinforced polymer appear in the flange portion 408.

FIG. 14 shows a cross sectional view of a hub portion 506 of a compositeconnector according to another example of the present disclosure. Thehub portion 506 is made from a pre-form net comprising a plurality oftabs, similarly to the composite connector 102 shown in FIG. 2 , suchthat the hub portion 506 comprises an inner layer 506 a featuring aplurality of joins and/or gaps 512 between the tabs. However, the hubportion 506 in this example further comprises an additional outer layer506 b, which comprises a rectangular support layer 509 (shown in FIG. 15) to which continuous fibre reinforcement 510 has been stitched, whichis wrapped around the inner layer 506 a. This reinforces the joinsand/or covers the gaps 512 in the inner layer 506 a, so that the hubportion 506 comprises no entirely non-reinforced regions of polymer.

The overwrapped outer layer 506 b confers additional advantages to thehub portion 506. The fibre reinforcement 510 in the outer layer 506 bextends continuously around substantially the entire circumference ofthe hub portion 506. This continuous circumferentially-oriented fibrereinforcement 510 may improve the hoop strength of the hub portion 506,as well as enabling better CTE and/or stiffness matching when theconnector is used with a composite fluid transfer conduit comprisingsimilarly circumferentially-oriented fibre reinforcement (not shown).

Alternatively, as shown in FIG. 16 , a hub portion 606 of a compositeconnector may comprise inner and outer layers 606 a, 606 b which eachcomprise tabbed pre-form nets similar to that seen in FIG. 3 or 6 . Theinner and outer layers 606 a, 606 b are angularly offset, such thatjoins or gaps in one layer are covered by the tabs of the other.

FIG. 17 shows an enlarged view of continuous fibre reinforcement 710 ina pre-form net 750. The pre-form net 750 is similar in structure to thatshown in FIG. 10 and comprises a common support layer 751 to which thecontinuous fibre reinforcement 710 is secured by being stitched thereto(although the stitching is not illustrated). FIG. 17 shows an enlargedview of the boundary 757 between a hub-forming portion 756 and aflange-forming portion 758 of the pre-form net 750.

As seen in FIG. 17 , slack 755 may be built into the continuous fibrereinforcement 710 at points near the boundary 757. The slack 755facilities bending the flange-forming portion 758 relative to the hubforming portion 756 when the pre-form net 750 is placed into a mould(not shown). The amount of slack required may be proportional inmagnitude to the distance of each section of continuous fibrereinforcement 710 from the centreline (not shown) of the flange-formingportion 758.

FIG. 18 shows, in cross-section, a three-stage tapered connector 802comprising a hub portion 806 which extends parallel to a central axis Cand a flange portion 808. The flange portion 808 comprises a taperingportion 808 a and a non-tapering portion 808 b. Continuous fibrereinforcement 810 (shown in FIG. 19 ) extends from the hub portion 806,through the tapering portion 808 a and into the non-tapering portion 808b of the flange portion 808.

A pre-form net 850 which may be used to form the tapered connector 802is shown in FIG. 19 . The pre-form net 850 comprises flange-formingportions 858 a, 858 b and a hub-forming portion 856. The flange-formingportions comprise a contiguous portion 858 a and a tabbed portion 858 bwhich extends from an edge of the contiguous portion 858 a. Thehub-forming portion 856 comprises a plurality of tabs which extend froman opposite edge of the contiguous portion 858 a.

The continuous fibre reinforcement 810 extends from the tabs of thehub-forming portion 856 into the contiguous and tabbed flange-formingportions 858 a, 858 b. The continuous fibre pre-form net 850 comprises aplanar common support layer 851, to which the continuous fibrereinforcement 810 is secured via stitching (not shown).

The composite connector 802 is formed by placing the pre-form net 850into a mould, with the contiguous portion 858 a rolled into afrustoconical shape around the central axis C to form the taperingportion 808 a of the flange portion 808. The tabs of the hub-formingportion 856 are bent outwards to form the tubular hub portion 806 andthe tabs of the tabbed portion 858 b are bent to be perpendicular to thehub-portion 806 to form the non-tapering flange portion 808 b. A polymermatrix is then introduced into the mould to form the composite connector802.

FIG. 20 shows an example of a mould 900 which may be used (e.g. asdescribed above) to form a composite connector according to one or moreexamples of the present disclosure.

The mould 900 comprises a base plate 902, a top plate 904 and inner andouter portions 906, 908. The inner and outer portions 906, 908 togetherdefine a cavity 909 which comprises a tubular hub-forming cavity 909 ainterconnected with an annular flange-forming cavity 909 b.

The base plate 902 comprises a polymer injection port 910 into whichliquid polymer may be injected into the cavity 909. The top plate 904comprises two outlets 912 which are connected to the cavity 909.

To form a composite connector, a continuous fibre pre-form net (e.g. oneof the pre-form nets shown in FIG. 3, 5, 7, 10, 13 or 19 ) is placedinto the mould 900 such that a hub-forming portion of said net is placedin the hub-forming cavity 909 a and a flange-forming portion of said netis placed in the flange-forming cavity 909 b.

Liquid polymer (e.g. a thermosetting polymer) is then introduced underpressure into the mould 900 via the polymer injection port 910. Thepressure under which the polymer is introduced and, optionally, a vacuumwhich may be applied at the outlets 912, draws the polymer through thecavity 909 and around and into the pre-form net. Once the polymer hasfilled the cavity 909 and fully permeated the continuous fibrereinforcement of the pre-form net, heat is applied to the mould 900 tocure the thermosetting polymer and form the completed compositeconnector. In examples wherein a thermoplastic polymer is injected intothe mould 900 then curing may not be necessary.

The completed connector may then be removed from the mould 909 (e.g. byremoving the bottom plate 902 and the outer portion 908).

FIG. 21 shows a perspective view of the composite connector 102 in use,connecting one end of a composite fuel pipe 104, comprising continuouscircumferentially-oriented fibre reinforcement 122, to a wing rib 118 ofan aircraft. The composite fuel pipe 104 extends into the hub portion106 and floats inside on an O-ring (not shown), which also serves toseal the connection. The connector 102 is secured rigidly to the spar118 via four bolts 120 (only three are visible in this Figure).

During flight, due to aerodynamic forces and/or temperature-basedexpansion/contraction, the wing rib 118 (and thus the connector 102) maymove relative to the fuel pipe 104. However, because the composite fuelpipe 104 floats on an O-ring, it is able to move relative to theconnector 102 without compromising the connection.

1. A composite connector for a fluid transfer conduit comprising: a hub portion comprising a tube which extends substantially parallel to a central axis; and a flange portion which extends from the hub portion at an angle to the central axis; wherein the hub portion and the flange portion each comprise a polymer reinforced with continuous fibre reinforcement and a common support layer to which the continuous fibre reinforcement is secured by being stitched thereto, the common support layer comprising a contiguous portion in the flange portion and a plurality of tabs in the hub portion, the plurality of tabs extending from an inner edge of the contiguous portion; wherein the continuous fibre reinforcement that is stitched to the common support layer comprises at least one continuous reinforcing fibre that extends circumferentially in the contiguous portion and into one or more of the plurality of tabs in the hub portion.
 2. The composite connector of claim 1, wherein the continuous fibre reinforcement comprises multiple layers stitched to the common support layer.
 3. The composite connector of claim 1, wherein the composite connector comprises a plurality of common support layers to which the continuous fibre reinforcement is secured by being stitched thereto.
 4. The composite connector of claim 1, wherein the hub portion comprises continuous circumferentially-oriented fibre reinforcement.
 5. The composite connector of claim 1, wherein the flange portion comprises at least one fixing point and the continuous fibre reinforcement is arranged to at least partially encircle the fixing point(s).
 6. The composite connector of claim 5, wherein the at least one fixing point is surrounded by unbroken fibre reinforcement.
 7. The composite connector of claim 5, further comprising a pair of adjacent fixing points and continuous fibre reinforcement encircling the pair of fixing points.
 8. The composite connector of claim 1, wherein the flange portion is substantially perpendicular to the central axis of the hub portion.
 9. The composite connector of claim 1, wherein the common support layer in the flange portion comprises: a tapering section comprising the contiguous portion; and a non-tapering section comprising a plurality of tabs extending from an outer edge of the contiguous portion; wherein the tapering section extends at a lesser angle to the central axis of the hub portion than the non-tapering section of the flange portion.
 10. The composite connector of claim 1, wherein the contiguous portion in the flange portion is annular.
 11. The composite connector of claim 1, wherein the at least one continuous reinforcing fibre that extends circumferentially in the contiguous portion and into one or more of the plurality of tabs in the hub portion extends radially along the one or more of the plurality of tabs.
 12. The composite connector of claim 1, wherein the hub portion comprises a plurality of separate segments of continuous fibre reinforcement corresponding to the plurality of tabs, the plurality of separate segments separated by regions of unreinforced polymer.
 13. The composite connector of claim 12, wherein the hub portion comprises a continuous fibre overwrap that extends around the hub portion to cover the regions of unreinforced polymer and to provide continuous circumferentially-oriented fibre in the hub portion.
 14. A connection system comprising: a composite connector as recited in claim 1; and a fibre-reinforced polymer fluid transfer conduit, the hub portion fitting onto or into the fluid transfer conduit.
 15. The connection system as claimed in claim 14, wherein the composition and orientation of the continuous fibre reinforcement at least within the hub portion is selected such that a stiffness of the hub portion substantially matches that of the fluid transfer conduit.
 16. The connection system as claimed in claim 14, wherein the composition and orientation of the continuous fibre reinforcement at least within the hub portion is selected such that a coefficient of thermal expansion of the hub portion substantially matches that of the fluid transfer conduit. 